GREEN BAY – Green Bay Packers running back Don Jackson’s season ended after making a cut on a typical outside zone play for the scout team Wednesday.

The rookie injured his left knee and within a couple of hours was placed on injured reserve.

“I saw everything when it happened,” running backs coach Ben Sirmans said. “Initially, I didn’t think anything of it and next thing I knew he wasn’t in. It was disappointing for the kid and obviously with us being in such a situation where we don’t have that many guys and he was just starting to come on.

“I felt bad for him, (it) just being a setback for him.”

Jackson said the doctors were going to re-do a scan later because there was so much swelling, they couldn’t see what the damage was. They told him they think it’s a cartilage tear, which probably would require surgery to repair.

Jackson, who was elevated from the practice squad before the Chicago game, had appeared in three games and carried 10 times for 32 yards. With the return of James Starks from a knee injury, Jackson was inactive against Tennessee and he was going to give ground to Christine Michael after he was claimed on waivers.

But the coaches like the 5-10, 208-pound undrafted rookie from Nevada and want to keep developing him. He was part of the off-season program but was cut before training camp because of a broken jaw.

He was signed to the practice squad after camp ended.

“You could see it more in practice, the game was starting to slow down a little bit more for him as opposed to just ‘bam’, the play starts and ‘Bam, I’m going full speed.’" Sirmans said. “You can go full speed, but mentally you have to make sure you’re processing everything the right way. You started to see that happen for him.”

The cordial Jackson said he couldn’t allow himself to mope around because it wouldn’t help his teammates fight their way out of a 4-5 hole.

“I’m not going to do anything that wouldn’t bring positive energy,” he said. “The guys have to get ready to play. I can’t be a bad apple by being mad.”

Cook progressing: This has been the first week that tight end Jared Cook has gotten a chance to work with the starting offense since suffering a high ankle sprain against Detroit in Week 3.

But it’s still not a lock that he’ll play against Washington. Asked if the veteran would be able to hit the ground running when he returns, tight ends coach Brian Angelichio said not to assume he would be ready this week.

“First we’ve got to see where he’s going to be when it comes to Sunday,” he said. “Those decisions haven’t been made. That’s an evaluation process that’s going on and by the end of the week I think we’ll know more. We’re just looking at each day with more improvement and we’ll see where he’s at as we get to Sunday.

Third and out: Quarterback Aaron Rodgers took the blame for throwing behind receiver Randall Cobb on the Packers’ first possession against the Titans, blowing an excellent opportunity to keep the first drive going.

Quarterbacks’ coach Alex Van Pelt said Rodgers’ release wasn’t good.

“His comment to me when he came off was, ‘The ball just got stuck in my hand,’” Van Pelt said. “That happens. It’s unfortunate. We had great field position and we had an easy third-down conversion to get us rolling and start us off.

“But those are little things that happen, but we have to be able to overcome those.”

Tight end nightmare: The defense allowed Tennessee tight end Delanie Walker to catch nine passes for 124 yards and a touchdown.

How in the heck are they going to defend Washington’s tight end duo of Jordan Reed and Vernon Davis, who have a combined 70 catches for 838 yards and five touchdowns?

“Well, you go back to work, and you know we just played against this team in the playoffs,” defensive coordinator Dom Capers said. “I thought our guys did a really good job against them. You know we played a lot of different combinations, and you were able to get pressure on the quarterback with four-man rush.

“And that's going to be something that will be critical on Sunday night.”

Injury report: Guard T.J. Lang (ankle) and linebacker Jake Ryan (ankle) both missed practice, making it less and less likely either will be able to play Sunday. Left tackle David Bakhtiari (knee) practiced on a limited basis and remains a question mark.

Running back Ty Montgomery returned to practice after a non-sickle cell-related illness. Center JC Tretter (knee) and cornerback Damarious Randall (groin surgery) did not participate.